In many applications, especially shipboard and aircraft applications, a high voltage direct current (DC) power is used to power motor controllers. Typically, a three phase alternating current (AC) voltage of 230 VAC (RMS voltage) is generated in a ship or an aircraft. The generated AC voltage is applied to an auto transformer rectifier unit (ATRU) and rectified to generate a voltage of ±270 VDC. The rectified DC voltage from the ATRU is then used to power the motor controllers. Other shipboard and aircraft applications, however, may require different DC output voltages. For example, multiple different voltage levels are required in modern aircraft for motor controllers in different zones. Higher voltages may be used in controlled pressure zones so as to reduce the size of feeder cables; whereas lower voltages are preferred in uncontrolled pressure zones so reduce the risk of corona, especially at higher altitudes. In addition, still other applications require an AC voltage.
In some power system configurations, use of separate power supplies and transformers to provide power for each of these different applications increases the size, cost, weight, and cooling requirements for the overall system, which is especially undesirable in aircraft applications. The placement of some power supplies and transformers limits the cooling to be air-cooled. Further, simply placing all of the various power supplies and transformers in a single area or compartment does not noticeably reduce the size, cost, weight, or cooling requirements for the overall system.